In current cellular radio networks, e.g., based on the LTE (Long Term Evolution) technology specified by 3GPP (3rd Generation Partnership Project), a radio device, typically referred to as a user equipment (UE), may establish a connection to the cellular radio network via one or more access nodes. Examples of such access nodes are base stations, in the LTE technology referred to as eNB (“evolved Node B”). Such connections may be controlled and managed by nodes of a core network part of the cellular radio network, e.g., an MME (Mobility Management Entity) or S-GW (Serving Gateway) of the LTE technology. The connection may use one carrier or multiple carriers, e.g., through carrier aggregation. In some case, the carriers may be selected from multiple available frequency layers.
When a UE wants to initiate a data transfer to or from the cellular radio network, typically first a signaling connection needs to be established. For example, in the LTE technology an RRC (Radio Resource Control) connection is established by the UE and the eNB. Once the RRC connection is established, the UE can send and receive traffic. The RRC connection may be kept active over multiple individual transfers of data, which means that it is not necessary to establish a new RRC connection for each transfer of data. Typically, the RRC connection is released after a certain period of inactivity, controlled by an inactivity timer. The setting of the inactivity timer is decided by the eNB and is typically is a trade-off between signaling load for setting up the RRC connection and resource availability for maintaining the RRC connection.
Whenever a UE requests a connection the network needs to decide whether and how to establish the connection. The decision whether to establish the connection is also referred to as “admission control”. The decision how to establish the connection may involve selecting a cell through which the connection is established, selecting a carrier for establishing the connection, or the like. These processes are typically implemented by connection management functionalities of one or more nodes of the cellular radio network, such as eNBs or MMEs.
However, it is a complex task to ensure that the connection management functionalities take the decisions which are most appropriate from the perspective of user experience and impact on performance of the cellular radio network. In many cases the decisions involve first deciding whether to admit establishment of the connection and, once the connection is established, later evaluating if the connection should be modified, e.g., by moving it to another access node or cell, switching the connection another carrier, releasing the connection, or the like. This may for example have the effect that some connections are not admitted even though their admission would have required only insignificant resources of the cellular radio network, or that connections are admitted which then turn out to require significant resources for handling the associated traffic or managing the connection. Further, the connection management functionalities may in some cases also set the inactivity timer to a value which is too high or to a value which is too low. A too high value of the inactivity timer may have the effect that the connection is maintained excessively long and resources are blocked. A too low value of the inactivity timer may in turn result in additional connection requests by the UE, the handling of which consumes resources both on the UE side and the cellular radio network side.
In 3GPP TS 36.331 V12.6.0 (2015-06), it is specified that the request for establishing the RRC connection, referred to as “RRCConnectionRequest message” may also include a field indicating an establishment cause. This information element may be used for prioritizing emergency calls or certain subscribers, or for distinguishing between different UE configurations. However, this information element provides only limited input to be used for taking appropriate connection management decisions when a regular application triggers establishment of a connection.
Accordingly, there is a need for techniques which allow for efficiently controlling connectivity of a radio device to a cellular radio network.